I've heard (or misheard) some native speakers pronounce "rt" like English "tch". An example is this Siri Nilsen song. At about 0:25, I believe she is saying "at alt blir klart", and it sounds for all the world to me just like an American would pronounce "clotch", were there such a word. Might that be what is making what sounds like sh-inn" instead of "sinn"? The "s" coming right after "tch"?

I wasn't thinking about the two-syllable thing, but yes, there is a glitch in the audio where there is a break in the pronunciation of "sinn". Can you comment "klart" being pronounced like "clotch"? The song is "Det som reparerer alt", if you have some other access to that other than via YouTube.